Rigged Mesh Behavior Is Different Despite Same Weights
If two vertices, even if near to each other, move differently, surely they have different weights.

When using automatic weighting, this common problem arise when some vertices get weight from some bones and other form more (or less) bones, so if you check only the head and the neck they seem similar, but in fact they are different.

In edit mode, if you select a group of vertices you can read the weights of the active one (last selected) in the N properties panel, so making a comparision between two vertices that have a different behaviour will underline where the problem lies.

An useful trick is to use the "selected to active" function, in which you select a group of vertices (like all bottom teeth), then shift select the vertex to follow (in my example it could be the center vertex), and press the little folder button (you have to do it for all the involved vertex groups, if some vertex group have influence on the selected vertices but not on the active, you have to use the remove button in the vertex weight tab).